sedimentary

Weathered iron-rich concretion or breccia

Goethite/hematite-bearing limonite concretion, possibly ferruginous sandstone

AI-generated identification · may be incorrect

The specimen appears rounded, tan-yellow, and strongly weathered, with a rough granular interior and dark brown-black iron-oxide patches. Likely hardness is about 4–6 Mohs, earthy to dull luster, no obvious cleavage, and moderate-to-high specific gravity; the exact mineralogy cannot be confirmed visually.

Identified August 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably formed when iron oxides cemented sand, clay, or rock fragments around a nucleus during groundwater alteration and weathering. Such concretions commonly form in sedimentary terrains from the Cenozoic to much older ages.

Uses & applications

Usually collected as a geological curiosity or used educationally; iron-rich material can be an ore when sufficiently concentrated, but this small specimen has no practical industrial value.

Geological facts

Yellow-brown coloration commonly reflects limonite/goethite, while black areas may be hematite or manganese oxides. A reddish-brown streak and attraction to a strong magnet would help distinguish iron-rich material.

Field identification & locations

Common in weathered sedimentary outcrops, soils, and gravel deposits worldwide. Test streak on unglazed porcelain, inspect for layered cement or sand grains, and compare weight with similarly sized ordinary rock.